The Mac have undergone any number of changes in their 40-odd-year history - with the rhythm section of Mick Fleetwood and John McVie the only constants - but generally their music falls into two incarnations: the 1960s "British blues boom" band led by the mercurial Peter Green, and the mid 70s-onwards Mac built around Christine McVie and Stevie Nicks's dreamy vocals, and Lindsay Buckingham's vision of building a songwriting catalogue as timeless as that of the Beach Boys or the Beatles. I love the second incarnation: it spawned the multimillion-selling Rumours, with its famous TV Grand Prix theme The Chain, pretty much defined Californian adult-oriented rock, and along the way spawned some of the most uproarious stories ever told about cocaine and rock'n'roll excess, as members married, divorced, got off with each other and developed fearsome problems with every substance short of the stuff you use to clean the kitchen. (My favourite story, which sadly I cannot possibly repeat here, involves Stevie Nicks, a billowing dress, powder, an onstage trap door, and a man armed with a straw.

They dominated 1970s radio. Whenever I bunked off from school, McVie's and Nicks's charms would be wafting out of the transistor, with songs like Don't Stop and Go Your Own Way. Their lyrics ("Thunder only happens when it's raining, Players only love you when they're playing") seemed to offer emotional truths, but from a place far removed from everyday existence. Even at that age I knew Fleetwood Mac did not come from Doncaster. For years, I imagined them all living together in some sort of giant, snow-encrusted fairy castle.

In those days virtually everyone - from the postman to local punks - understood that the Mac, though polished to a sheen, were the opposite of bland. Everyone owned Rumours and almost as many owned 1979's follow up, Tusk, a more experimental set containing a thunderous, percussive title track, and Sara, with its immortal line, "Down there, in the sea of love, where everyone would love to drown". Their 80s albums spawned other corkers, like Nicks's return to innocence Gypsy and Christine McVie's Little Lies.

But the 1960s outfit led by Peter Green (which I didn't discover until I was 26) was even better.

Green, Fleetwood and "Mac" (John McVie) came from the ranks of John Mayall's Bluesbreakers, but rapidly established their own band in a storm of blues-driven psychedelia. Guitarist Jeremy Spencer (who later joined a religious cult) was a pivotal figure at the start, although gradually the Mac became a vehicle for Peter Green's extraordinary playing and eerily powerful vocal introspection. Green plays and sings with an intensity of feeling far beyond most musicians. Black Magic Woman - their first hit single, from 1968 - is a brooding blues with an incendiary Green solo. A similar emotional power - and darkness - underpins the same year's Need Your Love So Bad. But this Mac had it all. They could unleash a fairly straight rock classic like Oh Well (Part One), and couple it with the aching B-side (Part Two), which demonstrated the supernatural beauty of Green's playing.

Perhaps my favourite ever Fleetwood Mac tracks are the sublime 1968 number one Albatross and Man of the World, much-nominated in a recent Readers Recommend. As rock'n'roll begat the rock'n'roll lifestyle, Green found himself confessing that he'd "had lots of pretty girls" but that the experience had left him hollow, sometimes wishing that he'd "never been born". The guitar playing is indescribably touching.

Around this time, Green was either being spiked with LSD or necking a heck of a lot of it. While his later Mac output reflects his mental deterioration, it is still incalculably great. When Green sings of "things I don't wanna see", you can hear a man imploding. He eventually withdrew from the band, and pretty much everything else. I was lucky enough to see a recovering Green six years ago in Sheffield, easing his way into Albatross, Black Magic Woman, an instrumental Man of the World and a coruscating I Believe My Time Ain't Long. Now he is silent again; apparently his medication has taken away his motivation for playing the guitar.

If or when the Mac return to stadiums next year, their most influential member will be absent. I could listen to and wallow in songs like Everyday, Little Lies, Dreams and Rhiannon all day, but the Green-era material is the stuff I'd choose to accompany me to the grave.